1 files changed, 23 insertions, 0 deletions
diff --git a/hw/nvram/fw_cfg.c b/hw/nvram/fw_cfg.c
index 08539a1aab..282ba93e2e 100644
--- a/hw/nvram/fw_cfg.c
+++ b/hw/nvram/fw_cfg.c
@@ -40,6 +40,7 @@
 #include "qemu/cutils.h"
 #include "qapi/error.h"
 #include "hw/acpi/aml-build.h"
+#include "hw/pci/pci_bus.h"
 
 #define FW_CFG_FILE_SLOTS_DFLT 0x20
 
@@ -1061,6 +1062,28 @@ bool fw_cfg_add_from_generator(FWCfgState *s, const char *filename,
     return true;
 }
 
+void fw_cfg_add_extra_pci_roots(PCIBus *bus, FWCfgState *s)
+{
+    int extra_hosts = 0;
+
+    if (!bus) {
+        return;
+    }
+
+    QLIST_FOREACH(bus, &bus->child, sibling) {
+        /* look for expander root buses */
+        if (pci_bus_is_root(bus)) {
+            extra_hosts++;
+        }
+    }
+
+    if (extra_hosts && s) {
+        uint64_t *val = g_malloc(sizeof(*val));
+        *val = cpu_to_le64(extra_hosts);
+        fw_cfg_add_file(s, "etc/extra-pci-roots", val, sizeof(*val));
+    }
+}
+
 static void fw_cfg_machine_reset(void *opaque)
 {
     MachineClass *mc = MACHINE_GET_CLASS(qdev_get_machine());